As to a conventional structure for mounting a power supply apparatus on a vehicle, U.S. Pat. No. 5,378,555, for example, discloses a battery pack for an electric vehicle (Patent Document 1). According to Patent Document 1, the battery pack includes a lower-tier battery nested in a supporting tray, and an upper-tier battery laid on the lower-tier battery.
Japanese Patent Laying-Open No. 11-89009 discloses a battery cooling structure for an electric vehicle that can improve the cooling efficiency of a battery without causing problems of the space for placement or structural complications (Patent Document 2). According to Patent Document 2, a direct current (DC)-DC converter converting a battery voltage into a prescribed voltage or the like is housed in a position surrounded by the battery within a battery case.
Connected to the battery pack as disclosed in Patent Document 1 are electrical components through which a high-voltage current flows, such as a converter stepping up or down a voltage output at a battery, a relay controlling a high-voltage circuit of the battery and an output cable of the battery. In a case where the battery is mounted between the driver's seat and the passenger's seat, however, these electrical components are located in the proximity of an instrument panel. Therefore, an electromagnetic wave emitted from the electrical components might cause a malfunction or noise of electronics provided at the instrument panel.